Vems install E12 M30B35 engine

[DMS]

I'm in the process of installing VEMS on my '78 BMW E12. I've fitted a M30B35 engine and ditched the original wiring, added a few sensors etc. For the wiring I have two wall mounted connectors so I can easily remove the engine in the future if this is needed.

On to the questions:
-Due to the number of pins on the wall-mount connector I wired the ground of CLT, IAT, TPS to a combined 4mm^2 ground wire. Can this cause problems?

-I want to connect the original ICV (three pins: open, 12V+, close) to the two free ignition out puts. Where can I find how to configure those? Or is it better to use an IGTB for these and use an ignition output for the boost solenoid (from the webshop)? (Atm I want to use an IGTB for the boost controller.)

Thanks,
Jan

[gunni]

I think your mixing a few things up

the ignition outputs will be IGBT´s.

You could use the last two injector outputs which will be FET´s. And then one IGBT for the boost control.

The sensor grounding you describe is the same way BMW does theirs so no worries.

[mattias]

The main problem with 4 mm^2 is that it's hard to crimp and use in most normal connectors.

Ultimately 4 mm^2 for the common sensor ground is way overkill, there will never be any current there (only milli-Amps).

The main concern for me is the longevity of the wires, use enough so that it doesn't break, I use 0.75 or 1 mm^2 for custom harnesses.

And yes, I think it's a good idea to splice the grounds together as you go, because there is no current going there you won't have any voltage drop that will affect the sensor reading either. It will make the harness easier to work with in the end. The same goes for the injectors, you can feed them with +12V using a 1.5-2.0 mm^2 wire which split up as close to the connectors as possible.


As far as what outputs to use for what purpose, I use the two remaining injector FETs for the 3-pin ICV. I use the IGBTs (ignition) for pulling all the accessory relays (fuel, fan, ..). I don't trust the low current P259 outputs, and never will.

[DMS]

Thanks Gunni, You're right about the mixxing stuff ..

Do you know which pin has the open-function and which has the close function on the ICV?

Mattias:
The wall-mount connector I used has 4 pins for wires up to 6 mm^2. I used 4mm^2 for:
-injectors 12V+
-12V+ (ICV, feed to dP sensor)
-ground to head
-comon ground sensors (CLT, IAT, TPS)

All other wires are 0.75 mm^2 except for VR and Hall since these sensor wires were smaller in stock form. Both trigger wires are shielded ofcourse. Shield from both wires are connected to a separate ground point opposed to the common sensor ground. Should I add a condensator between ground and shield aswell? (Incase of high frequency noise?)

The LPG system will get the same wall mount connector and the same wiring strategy.

I took no risk with feed, ground and shield for important sensors/actuators like WBO2, triggers, and coils and wired these separatelly from to the fuse box, common ground etc.

[gunni]

Right now I can´t remember, but you can switch them around in the EC36 connector easy enough. Of course you should be able to do this in the config but at the moment the second icv channel needs to follow the first one.

[DMS]

That's good to know. Is there an easy/good way I can test the pins on the bench?

[mattias]

I wouldn't bother, just swap the wires or invert the function in the software. Easy enough.

How are you handling the VR sensor shield and ground?

[DMS]

Both GND and shield to common ground at the ECU side. Shield loose at the sensor side.

[mattias]

Does the wall-mount connector support feeding the shield through that way?

[DMS]

The sensor wire is split just before the connector with each wire connected to a separate pin. ECU and Common ground are within 10 cm of the connector. I'm not adding much extra length with the wall mount connector opposed to the original wiring situation of the motronic.

[DMS]

Should I connect any additional flyback with the following setup:

Inj (FET) A,B,C,D,E,F to fuel injectors
Inj (FET) G, H to ICV

12V+ to the ICV will be connected to the same source as the injectors:



IGN (IGBT) A,B,C to wasted spark coils
IGN (IGBT) D to fuelpump relay
IGN (IGBT) E to FAN relay
IGN (IGBT) F to boost solenoid
Switched 12V+ directly from the fusebox (thee different fuses: coils, fuel+fan, solenoid).

In the manual there is no flyback for the IGBT's pictured. However for the boost solenoid I found the advice to apply a flyback diode. Should I connect flybacks for these 12V+ feeds aswell, and if so should these also be connected to EC36p23?

To me it seems the flyback for the injectors also serves for a flyback for the other 12V+ feeds since these are all connected to the battery + in the end. But then rises the question why the flyback in the picture above is not in front of the fuse?

Ps. I assume a 1N4007 diode would do the job just fine? (I'll not connect this one since my vems unit has the diode internally).